The present invention relates to replaceable tools for agricultural implements and, more specifically, to knock-on tools such as knock-on sweeps which are received over and retained by a wedge-shaped support or adapter on a shank or other tool support.
With at least most previously available tillage tool quick change systems, properly mating the sweep with the adapter has been a continuing source of difficulty. Inability to hold tight manufacturing tolerances, particularly during forging or casting processes and during formation of the engaging surfaces on the sweep stem, can result in an overly loose fit which results in lost sweeps, or an excessively tight fit between the adapter and the mating portion so that mounting the sweep requires much force. The problems with fit are magnified, for example, when one of the mating components is undersized and the other component is oversized. With most available structures, optimizing the sweep-adapter contact surface is difficult or impossible. Since sweep-adapter contact provides primary retention and support for the sweep, a poor sweep-adapter contact results in a loose mounting or difficulty in mounting the sweep and inadequate sweep retention.
Because of the sweep forming process used during manufacture, the lower portions of many knock-on sweep stems roll out or widen causing the spacing between the engaging surfaces at the bottom of the stem to increase. This widening of the lower engaging surfaces increases the potential for sweep loss during operation since forces tending to rip the sweep from the adapter act primarily near the bottom of the stem.
To provide optimum sweep support and retention, eight contact points or four contact pair locations between the adapter and the engaging surfaces of the sweep stem must be established. The stem roll out or widening requires the sweep be driven farther onto the adapter before such eight-point contact can be made. Vertical variations in the final sweep mounting locations can cause unacceptable variations in the depth of penetration of the sweeps across the implement.
It is therefore an object of the present invention to provide an improved adapter for a knock-on sweep or similar earthworking tool. It is a further object to provide such an adapter which overcomes most or all of the aforementioned problems.
It is another object of the present invention to provide an improved adapter for a knock-on sweep or similar earthworking tool which provides more reliable and more predictable sweep-adapter contact for better retention and support. It is another object to provide such an adapter which improves sweep-adapter fit at locations where forces tending to remove the sweep from the adapter are localized.
To optimize the surface contact between a sweep stem and an adapter, upper and lower contact surfaces on each side of the adapter are configured to provide differential widening. The rate of change of distance between opposite upper surfaces is greater than the rate of change of the distance between the lower surface in a direction towards the widest portion of the wedge. As the width of the adapter decreases from the widest end towards the narrowest end to define the wedge, the lower surfaces narrow at a lesser rate to hasten contact between the lower contact surfaces and lower wrap around portion on the stem.
In one embodiment, each side of the adapter includes first and second generally planar surfaces intersecting at an edge and forming a compound angle. As the width of the adapter decreases from the widest end towards the narrowest end to define the wedge, the lower surfaces narrow at a lesser rate than that of the upper surfaces. The compound angle structure results in an increased effective width at the narrow lower end of the adapter as the contact surfaces are engaged by the lower wrap around portion of the stem. The increased effective width defined by the differential widening in the direction of the wedge assures engagement of all the desired contact points earlier and at a more predictable location than with a standard straight wedge configuration typical of the prior art devices.
In the embodiment described below, the adapter is fabricated as a casting to facilitate incorporation of a compound angle design. The adapter compound angle creates a better sweep-adapter mating surface structure to increase the wedge between the mating surfaces and provides improved spaced contact point locations for stability. The improved wedge therefore results in superior sweep retention and a firmer connection between the sweep and the adapter. Problems of inability to easily slip the sweep on the adapter and improper fit between the sweep and adapter are substantially reduced or eliminated. The adapter compound angle compensates for unpredictable complex shape formations created during the formation of the engaging surfaces on the stem of the sweep. The compound surface design is particularly useful with sweep retaining structures which rely on operating forces to wedge the sweeps in a final mounted position and thereby allow sweeps to be hand mounted without substantial force.
These and other objects, features and advantages of the present invention will become apparent from the description below in view of the drawings.